-해서요 is a respectful form of -해서, which means 'because.' 예) 저는 오늘 이 사전을 샀어요. 친구들이 권해서요. I bought this dictionary today because my friends recommended it. 저는 어제 티아와 심한 말싸움을 했어요. 저를 자꾸 놀려서요. I had a fierce argument with Tia yesterday because she kept teasing me. 도움이 되시길...

해서요 is the verb 하다's connective form 해서 suffixed with the politeness indicator -요. It is constructed as 하다(do) + -아/어 + 서, where the -아/어 is one of the most common conjugational forms. -아/어 connects a verb with another word or a phrase, giving a reason, condition, or background for what follows. -(아/어)서 with the 서 additive to express "in that base/position" is used very widely with all kinds of verbs. 해서 is just one example of them. For example: - 밥을 하다(cook a meal) + 식탁 위에 두다(leave it on the table) => 밥을 해서 식탁 위에 두다 (simple "and" connection) - 비가 왔다(it rained) + 소풍을 가지 못했다(couldn't go on a picnic) => 비가 와서 소풍을 가지 못했다 (a reason) Your homework might be expecting -해서 to be used as a sentence ending (judging from "ending" and "요"). -해서, a connective form of certain -하다 verbs, is not designed for sentence endings but may be used as such. (There's 하다, and others ending with this form, like 말하다. Plain 하다 is unlikely to come at the end of a sentence) Here are some examples. AA: 왜 그런 말씀 하세요? (Why do you say such a thing?) BB: 미안해서요. (Because I feel sorry) * 미안하다(sorry) -> 미안해서요. Mother: 너 아침 안 먹고 그냥 나가니? (Are you going out without eating breakfast?) Son: 버스 시간에 늦어서 급해서요. (Yes, because I'm in a big hurry to catch the bus) * 급하다(in a hurry) -> 급해서요. -지 모르다 = We don't know if ... = It might/could be that ... (expresses a weaker guess, or conjecture). 모르다 (do not know <-> 알다 = know) is the dictionary form, before it takes on an applicable form. -지, which follows a phrase or a clause, constructs the fact that's in question, very much like "whether ...". Here are -지 모르다 in various sentence ending forms. (the four most basic ones) - 그것이 사실일지 모릅니다. (It might be that it's true) Formal, and polite. - 그것이 사실일지 모른다. Formal, plain sounding. - 그것이 사실일지 몰라요. Informal, polite. - 그것이 사실일지 몰라. Informal, plain. - 그것이 사실일지 모르겠다. (It is possible that it's true) -겠 adds more uncertainty, making it weaker than -지 모른다.

You may want to try dic.naver.com for looking up Korean word definition and examples. It's hard to understand for non-Koreans, but you can find examples at least. There are 2 meanings for "-지 모르다" in the dictionary 1) Meaning : May(might) ~ (Guessing or Questioning things/events that are uncertain.) Example: 친구가 화났을지(도) 모른다. (The friend may be angry) --> 2) Meaning : You cannot imagine know how ~ = ~ so ~ that ~ 바라던 대학에 붙어서 얼마나 기쁜지 모른다. (You cannot imagine how happy I am because I am admitted to the university that I want.) And as you might know, 몰라요/모르겠어요 is the different forms of "모르다" and it only changes the tastes of word and degree of politeness. Meaning doesn't change. This is the original result that you can find when you look up "모르다' from dic.naver.com Hope my explanation helps you. ================================= 「-ㄴ지」 1 . Meaning: (의문사 없이 쓰여) 불확실한 사실에 대한 짐작이나 의문의 뜻을 나타낸다. Examples: 친구가 화났을지도 모른다. 그 사람은 이미 죽었을는지 모른다. 과연 우리가 가게 될는지 모르겠다. 2 . Meaning: (‘얼마나, 어찌’ 따위와 함께 쓰여) 감탄적으로 강조하여 ‘매우 그러하다’ 또는 ‘매우 그리하다’의 뜻을 나타낸다. Examples: 바라던 대학에 붙어서 얼마나 기쁜지 모른다. 육개장이 얼마나 매운지 몰라. 우리 아들 녀석은 어찌나 잘 뛰는지 몰라. ================================= Seokbae